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  • 1
    Electronic Resource
    Electronic Resource
    Seed survival and predation of Anoda cristata in soyabean crops (2005)
    Oxford, UK : Blackwell Science Ltd
    Weed research 45 (2005), S. 0 
    Details
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Anoda cristata is a troublesome annual broad-leaved weed in summer crops in the rolling Pampa in Argentina; seeds are the only source of regeneration of this species. Seed persistence or depletion is the result of survival and loss processes, including predation. The objective of this study was to determine survival at two burial depths in undisturbed soil and predation rates of A. cristata seeds in soyabean crops in different rotations and tillage systems. Survival was discontinuous and decreased to 25% after 35 months, after which no further reduction in survival was observed to the end of the experiment at 96 months. No differences in seed survival between seeds placed on the soil surface and buried 5 cm below the soil surface were found at 80 months, but at later times survival was lower for seeds placed on the soil surface. Predation rates ranged between 0.3% day−1 and 6.7% day−1. Of the models tested, a polynomial regression of the rate of predation with time gave the best representation of seed predation. From January to July, predation was higher in non-tillage plots in the wheat/soyabean rotation. There was no significant difference in predation rates between tillage systems in the soyabean monoculture and no difference between planting densities. Higher crop residue levels in non-tillage plots in the wheat/soyabean rotation was the dominant factor influencing seed predation, probably because such habitat favours the presence of seed predators.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3180.2005.00474.x
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  • 2
    Electronic Resource
    Electronic Resource
    Demography of Anoda cristata in wide- and narrow-row soyabean (2002)
    Oxford, UK : Blackwell Science Ltd
    Weed research 42 (2002), S. 0 
    Details
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The annual weed Anoda cristata is recognized as a problem of increasing importance in soyabean crops. As seeds are the only source for the renewal of A. cristata populations, knowledge of its seedbank characteristics and seed production is useful in improving weed management decisions. There is a lack of information about the effect of the planting pattern of soyabean on weed population dynamics. The effects of 70-cm and 35-cm soyabean row spacings on A. cristata seedbank, seedling recruitment and mortality, plant biomass, seed production and seed shed were determined. Soyabean density was higher in 35-cm row spacings as an increase in planting rate in narrow-row soyabean is recommended for producers in Argentina. The different planting patterns modified A. cristata demography through changes in plant biomass and, subsequently, in seed production. Seedling emergence, plant mortality and the pattern and duration of seed shed were similar in both planting patterns and thus independent of crop spatial arrangement and density. Increments in A. cristata seedbank can be reduced by planting soyabean at narrower row spacings and by bringing forward soyabean harvest. The first practice reduces A. cristata biomass and consequently seed production, and the second practice decreases the amount of seeds contributing to the soil seedbank.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3180.2002.00307.x
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  • 3
    Electronic Resource
    Electronic Resource
    Anoda cristata control with glyphosate in narrow- and wide-row soyabean (2004)
    Oxford, UK : Blackwell Science Ltd
    Weed research 44 (2004), S. 0 
    Details
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Experiments evaluated the effect of glyphosate rate and Anoda cristata density, on crop and weed biomass and weed seed production in wide (70 cm) and narrow rows (35 cm) glyphosate-resistant soyabean (Glycine max). Soyabean density was higher at 35 cm row spacing as an increase in planting rate in narrow-row soyabean is recommended for producers in Argentina. Soyabean biomass at growth stage V4 (four nodes on the main stem with fully developed leaves beginning with the unifoliate leaves) was higher when grown on narrow than in wide-rows but was not affected by the presence of A. cristata. At growth stage R5 (seed initiation – seed 3 mm long in a pod at one of the four uppermost nodes on the main stem, with a fully developed leaf and full canopy development), crop biomass was greater in narrow rows compared with wide rows with 12 plants m−2 of A. cristata. In narrow-row soyabean, a single application of a reduced rate of glyphosate maintained soyabean biomass at R5 and provided excellent weed control regardless of weed density. In wide-row soyabean control was reduced at the high weed density. Regardless of row spacing, A. cristata biomass and seed production were severely reduced by half of the recommended dose rate of glyphosate but the relationship between biomass and seed production was not altered. Glyphosate rates as low as 67.5 g a.e. ha−1 in narrow rows or 540 g a.e. ha−1 in wide rows provided excellent control of A. cristata. To minimize glyphosate use, planting narrow-row soyabean are effective where A. cristata density is low.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3180.2004.00379.x
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  • 4
    Electronic Resource
    Electronic Resource
    Response of Elodea canadensis Michx, and Myriophyllum spicatum L. to shade, cutting and competition in experimental culture (1996)
    Springer
    Hydrobiologia 340 (1996), S. 219-224 
    Details
    ISSN: 1573-5117
    Keywords: weed control ; competition ; disturbance ; Elodea canadensis ; Myriophyllum spicatum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Elodea canadensis Michx. and Myriophyllum spicatum L. are widespread nuisance aquatic plant species. Their ecology is regarded as similar. Both species have been previously classified in terms of established-phase survival strategy as ‘competitive disturbance-tolerant’ species. Experimental data are presented to show that although this broad categorisation of strategy is probably correct for the two species, it is possible to demonstrate significant differences in terms of response to disturbance and competition. Less difference was discernible in their comparative response to stress. The drawbacks of applying broad descriptive terminology when dealing with two species of similar strategy are addressed. The results help explain reports of variable success in attempting to manage these two species using disturbance-based weed control measures, and suggest that Elodea is even less susceptible to such measures than Myriophyllum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00012758
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  • 5
    Electronic Resource
    Electronic Resource
    Submerged plant survival strategies in relation to management and environmental pressures in drainage channel habitats (1996)
    Springer
    Hydrobiologia 340 (1996), S. 191-195 
    Details
    ISSN: 1573-5117
    Keywords: Submerged plants ; survival strategies ; drainage channels ; aquatic weeds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The abundance of submerged weeds, in relation to management regime and environmental factors, was surveyed during 1992 and 1993 in drainage channels located in four geographically-distinct areas of Britain. The aim of the study was to ascertain, using a multivariate approach, the degree to which species survival strategy and vegetation could be related to disturbance and stress pressures on plant survival. Indices of disturbance and stress were constructed from combined environmental data for each site. A species ordination using Canonical Correspondence Analysis showed that the combined disturbance variable explained more of the variability that did stress. Two main groups of species could be distinguished. The larger group scored low on the disturbance gradient and these species, with different tolerances to stress (especially light-limitation), appeared to be those better-adapted to habitats with low disturbance (e.g. Potamogeton pectinatus and Potamogeton lucens). The smaller group comprised species which tended to occur in sites with higher disturbance (e.g. regular cutting) such as Callitriche stagnalis. Using the terminology of strategy theory, most of the dominant species could be classed as ‘competitive/disturbance tolerators (CD)’ or variants of this established-phase strategy. The limitations are discussed of applying the strategy approach at species level in a defined habitat-type which shows a high degree of uniformity between sites, such as artificial drainage channels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00012754
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  • 6
    Electronic Resource
    Electronic Resource
    Propagule bank and plant emergence of macrophytes in artificial channels of a temperate irrigation area in Argentina (1999)
    Springer
    Hydrobiologia 415 (1999), S. 1-5 
    Details
    ISSN: 1573-5117
    Keywords: submerged plants ; macrophytes ; propagule bank ; irrigation and drainage channels ; south America ; aquatic weeds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The irrigation district of the lower valley of Río Colorado (62° 37′ W, 39° 23′ S) was examined during 1995 and 1996 to evaluate propagule bank abundance and regeneration in five irrigation and five drainage channel sites. Six 15 cm deep cores from each site were collected in late winter and sectioned into two subsamples. One was sieved to identify taxa and propagule density and the other was placed under controlled laboratory conditions to record emergence over 90 days. Mean propagule density of Potamogeton pectinatus (260 tubers. m-2, 173 rhizome nodes. m-2 and 246 seeds. m-2) and Zannichellia palustris (968 seeds. m-2) was higher in irrigation than in drainage channels. By contrast, higher values in drainage channels were recorded for Ruppia maritima (4352 seeds. m-2) and Chara contraria (35633 oospores. m-2). Plant emergence in P. pectinatus was independent of channel type. Higher and lower values were registered in irrigation channels for Z. palustris and the other two species, respectively. Plant emergence in relation to propagule density for all the species ranged from 24% to 56%, and no differences were found between irrigation and drainage channels. Results are discussed in relation to the established vegetation and the different management and environmental conditions of both types of channels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003808713907
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  • 7
    Electronic Resource
    Electronic Resource
    Interrelationships of fish and channel environmental conditions with aquatic macrophytes in an Argentine irrigation system (1998)
    Springer
    Hydrobiologia 380 (1998), S. 15-25 
    Details
    ISSN: 1573-5117
    Keywords: Macrophytes ; irrigation and drainage channels ; turbidity ; Cyprinus carpio ; South America
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study examines the relationships between fish, environmental variables and submerged macrophytes within the irrigation system of the lower valley of the Río Colorado in southern Argentina. Using Canonical Correspondence Analysis (CCA), the strongest environmental gradients detected were conductivity and carp ( Cyprinus carpi) biomass per unit area of channel cross-section. These variables were positively associated with each other and also with water turbidity. Sites scoring high on these gradients were mainly drainage channels; those scoring lowest were irrigation channels. The main fish species associated with high carp biomass, high turbidity and high conductivity were carpa ( C. carpio), pejerrey ( Odontesthes bonariensis), madrecita ( Jenynsia lineata lineata) and lisa ( Mugil liza). Dientudo ( Oligosarcus jenynsi) and mojarra ( Astianax eigenmanniorum) were more strongly associated with clearer water, with low carp biomass. In all CCA analyses macrophytes were arranged in similar order along the main conductivity-turbidity-carp biomass gradient. Lowest on this main environmental gradient, and scoring very close to each other, were Potamogeton pectinatus and Chara contraria. Salinity-tolerant species such as Ruppia maritima, Zannichellia palustris and Enteromorpha flexuosa tended to score highest, followed by the surface floating Azolla filiculoides and the filamentous alga Cladophora surera. Within the constraints imposed by conductivity, turbidity was a key predictor of both abundance and distribution of the two dominant plants of the irrigation scheme ( P. pectinatus and C. contraria). Turbidity was strongly predicted by biomass of carp per unit channel cross sectional area, when fine sediment particle content was taken into account. The positive association between carp biomass and water turbidity was both substantial and predictable, and was in turn associated with reduction in submerged plant growth. The biomass of the most widespread nuisance-causing plant species in the channels, Potamogeton pectinatus, could best be predicted ( R = 0.592, P 〈 0.05) using a multiple regression model utilising four predictor variables: conductivity, nitrate, phosphate and carp biomass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003215513435
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